Vagal stimulation

Abstract

The disclosure herein relates generally to methods for treating heart conditions using vagal stimulation, and further to systems and devices for performing such treatment. Such methods may include monitoring physiological parameters of a patient, detecting cardiac conditions, and delivering vagal stimulation (e.g., electrical stimulation to the vagus nerve or neurons having parasympathetic function) to the patient to treat the detected cardiac conditions.

What is claimed is: 
     
       1. A device for delivering vagal stimulation comprising:
 monitoring apparatus configured to monitor physiological parameters of a patient, wherein the monitoring apparatus comprises at least one electrode to monitor the electrical activity of the patient's heart; 
 a sensing module coupled to the monitoring apparatus and configured to receive the monitored physiological parameters; 
 a therapy delivery module configured to deliver electrical stimulation to the patient's vagus nerve and to deliver ventricular arrhythmia therapy to patient's heart; and 
 a control module coupled to the sensing module and to the therapy delivery module and configured to:
 detect a supraventricular tachycardia using the monitored physiological parameters, 
 initiate delivery of electrical stimulation to the patient's vagus nerve upon detecting the supraventricular tachycardia, 
 analyze the monitored physiological parameters after the delivery of electrical stimulation to the patient's vagus nerve, 
 adjust the electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameters, 
 terminate the delivery of electrical stimulation to the patient's vagus nerve after exhausting adjustments to the electrical stimulation delivered to the patient's vagus nerve, and 
 initiate delivery of ventricular arrhythmia therapy to the patient's heart following the termination of the delivery of electrical stimulation to the patient's vagus nerve after the exhaustion of adjustments. 
 
 
     
     
       2. The device of  claim 1 , wherein the control module is further configured to control the delivery of electrical stimulation to the patient's vagus nerve to be synchronized to blanking periods associated with either of the P-waves or the R-waves within the electrical activity of the patient's heart. 
     
     
       3. The device of  claim 2 , wherein the control module is further configured to adjust the electrical stimulation by changing the synchronization of the delivery of the electrical stimulation from synchronization with a blanking period associated with one of either of the P-waves or the R-waves to synchronization with the blanking period associated with the other. 
     
     
       4. The device of  claim 1 , wherein the control module is further configured to control the execution of at least one of:
 adjusting the electrical stimulation if the R-R intervals within the electrical activity of the patient's heart have not changed in response to the delivery of electrical stimulation to the patient's vagus nerve, 
 adjusting the electrical stimulation if the P-R intervals within the electrical activity of the patient's heart have not changed in response to the delivery of electrical stimulation to the patient's vagus nerve, and 
 adjusting the electrical stimulation if the morphology of the R-waves of the electrical activity of the patient's heart has not changed in response to the delivery of electrical stimulation to the patient's vagus nerve, 
 wherein exhausting the adjustments to the electrical stimulation delivered to the patient's vagus nerve comprises determining that the adjustments have not changed at least one of the R-R intervals, the P-R intervals, and the morphology of the R-waves of the electrical activity of the patient's heart. 
 
     
     
       5. The device of  claim 1 , wherein the control module is further configured to control the execution of at least one of:
 increasing the electrical stimulation if the R-R intervals within the electrical activity of the patient's heart are less than a first selected value, wherein increasing the electrical stimulation comprises at least one of increasing the voltage of the electrical stimulation, increasing the frequency of the electrical stimulation, increasing the pulse width of each pulse of the electrical stimulation, and increasing the number of pulses per burst of pulses of the electrical stimulation, and 
 decreasing the electrical stimulation if the R-R intervals within the electrical activity of the patient's heart are greater than a second selected value, wherein decreasing the electrical stimulation comprises at least one of decreasing the voltage of the electrical stimulation, decreasing the frequency of the electrical stimulation, decreasing the pulse width of each pulse of the electrical stimulation, and decreasing the number of pulses per burst of pulses of the elecptrical stimulation. 
 
     
     
       6. A device for delivering vagal stimulation comprising:
 monitoring apparatus configured to monitor physiological parameters of a patient, wherein the monitoring apparatus comprises at least one electrode to monitor the electrical activity of the patient's heart; 
 a sensing module coupled to the monitoring apparatus and configured to receive the monitored physiological parameters; 
 a therapy delivery module configured to deliver electrical stimulation to the patient's vagus nerve; and
 a control module coupled to the sensing module and to the therapy delivery module and configured to: 
 detect a supraventricular tachycardia using the monitored physiological parameters, 
 initiate delivery of bursts of electrical stimulation to the patient's vagus nerve upon detecting indication of a supraventricular tachycardia, wherein each burst of electrical stimulation comprises one or more pulses, 
 analyze the monitored physiological parameters after the delivery of electrical stimulation to the patient's vagus nerve, and 
 adjust the bursts of electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameter, wherein adjusting the bursts of electrical stimulation comprises at least one of changing the voltage of the bursts of electrical stimulation, changing the frequency of the bursts of electrical stimulation, changing the pulse width of each pulse of the bursts of electrical stimulation, and changing the amount of pulses per burst of pulses of the bursts of electrical stimulation. 
 
 
     
     
       7. The device of  claim 6 , wherein the control module is further configured to control the delivery of the bursts of electrical stimulation to the patient's vagus nerve to be synchronized to blanking periods associated with either of the P-waves or the R-waves within the electrical activity of the patient's heart. 
     
     
       8. The device of  claim 7 , wherein the control module is further configured to adjust the bursts of electrical stimulation by changing the synchronization of the delivery of the bursts of electrical stimulation from synchronization with a blanking period associated with one of either of the P-waves or the R-waves to synchronization with the blanking period associated with the other. 
     
     
       9. The device of  claim 6 , wherein the control module is further configured to control the execution of at least one of:
 adjusting the bursts of electrical stimulation if the R-R intervals within the electrical activity of the patient's heart have not changed in response to the delivery of the bursts of electrical stimulation to the patient's vagus nerve, 
 adjusting the bursts of electrical stimulation if the P-R intervals within the electrical activity of the patient's heart have not changed in response to the delivery of the bursts of electrical stimulation to the patient's vagus nerve, and 
 adjusting the bursts of electrical stimulation if the morphology of the R-waves of the electrical activity of the patient's heart has not changed in response to the delivery of the bursts of electrical stimulation to the patient's vagus nerve. 
 
     
     
       10. The device of  claim 6 , wherein the control module is further configured to control the execution of at least one of:
 increasing the bursts of electrical stimulation if the R-R intervals within the electrical activity of the patient's heart are less than a first selected value, wherein increasing the bursts of electrical stimulation comprises at least one of increasing the voltage of the bursts of electrical stimulation, increasing the frequency of the bursts of electrical stimulation, increasing the pulse width of each pulse of the bursts of electrical stimulation, and increasing the number of pulses per burst of the bursts of electrical stimulation, and 
 decreasing the bursts of electrical stimulation if the R-R intervals within the electrical activity of the patient's heart are greater than a second selected value, wherein decreasing the bursts of electrical stimulation comprises at least one of decreasing the voltage of the bursts of electrical stimulation, decreasing the frequency of the bursts of electrical stimulation, decreasing the pulse width of each pulse of the bursts of electrical stimulation, and decreasing the number of pulses per burst of the bursts of electrical stimulation. 
 
     
     
       11. A method of delivering vagal stimulation comprising:
 monitoring physiological parameters of a patient, wherein the physiological parameters comprise the electrical activity of the patient's heart; 
 detecting a supraventricular tachycardia using the monitored physiological parameters; 
 delivering electrical stimulation to the patient's vagus nerve upon detecting the supraventricular tachycardia; 
 analyzing the monitored physiological parameters after delivering electrical Stimulation to the patient's vagus nerve; 
 adjusting the electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameters; 
 terminating the delivery of electrical stimulation to the patient's vagus nerve After exhausting the adjustments to the electrical stimulation delivered to the patient's vagus nerve; and 
 delivering ventricular arrhythmia therapy to the patient's heart after terminating The delivery of electrical stimulation to the patient's vagus nerve. 
 
     
     
       12. The method of  claim 11 , wherein the delivery of electrical stimulation to the patient's vagus nerve is synchronized to blanking periods associated with either of the P-waves or the R-waves within the electrical activity of the patient's heart. 
     
     
       13. The method of  claim 12 , wherein adjusting the electrical stimulation comprises changing the synchronization of the delivery of the electrical stimulation from synchronization with a blanking period associated with one of either of the P-waves or the R-waves to synchronization with the blanking period associated with the other. 
     
     
       14. The method of  claim 11 , wherein adjusting the electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameters comprises at least one of:
 adjusting the electrical stimulation if the R-R intervals within the electrical activity of the patient's heart have not changed in response to the delivery of electrical stimulation to the patient's vagus nerve, 
 adjusting the electrical stimulation if the P-R intervals within the electrical activity of the patient's heart have not changed in response to the delivery of electrical stimulation to the patient's vagus nerve, and 
 adjusting the electrical stimulation if the morphology of the R-waves of the Electrical activity of the patient's heart has not changed in response to the delivery of electrical stimulation to the patient's vagus nerve, 
 wherein exhausting the adjustments to the electrical stimulation delivered to the patient's vagus nerve comprises determining that the adjustments have not changed at least one of the R-R intervals, the P-R intervals, and the morphology of the R-waves of the electrical activity of the patient's heart. 
 
     
     
       15. A method of delivering vagal stimulation comprising:
 monitoring physiological parameters of a patient, wherein the physiological parameters comprise the electrical activity of the patient's heart and at least one of the chemical activity of the patient's heart, the hemodynamic activity of the patient's heart, and the electrical activity of the patient's vagus nerve; 
 detecting a supraventricular tachycardia using the monitored physiological parameters; 
 delivering bursts of electrical stimulation to the patient's vagus nerve upon Detecting indication of a supraventricular tachycardia, wherein each burst of electrical stimulation comprises one or more pulses; 
 analyzing the monitored physiological parameters after delivering electrical stimulation to the patient's vagus nerve; and 
 adjusting the bursts of electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameters, wherein adjusting the bursts of electrical stimulation comprises at least one of changing the voltage of the bursts of electrical stimulation within a range of about 1 volt and about 8 volts, changing the frequency of the bursts of electrical stimulation within a range of about 1 hertz to about 50 hertz, changing the pulse width of each pulse of the bursts of electrical stimulation within a range of about 0.2 milliseconds to about 1 milliseconds, and changing the number of pulses per burst of the bursts of electrical stimulation within a range of about 3 pulses to about 20 pulses. 
 
     
     
       16. The method of  claim 15 , wherein the delivery of the bursts of electrical stimulation to the patient's vagus nerve is synchronized to blanking periods associated with either of the P-waves or the R-waves within the electrical activity of the patient's heart. 
     
     
       17. The method of  claim 16 , wherein adjusting the electrical stimulation comprises changing the synchronization of the delivery of the bursts of electrical stimulation from synchronization with a blanking period associated with one of either of the P-waves or the R-waves to synchronization with the blanking period associated with the other. 
     
     
       18. The method of  claim 15 , wherein adjusting the electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameters comprises at least one of:
 adjusting the bursts of electrical stimulation if the R-R intervals within the Electrical activity of the patient's heart have not changed in response to the delivery of the bursts of electrical stimulation to the patient's vagus nerve, 
 adjusting the bursts of electrical stimulation if the P-R intervals within the Electrical activity of the patient's heart have not changed in response to the delivery of the bursts of electrical stimulation to the patient's vagus nerve, and 
 adjusting the bursts of electrical stimulation if the morphology of the R-waves of the electrical activity of the patient's heart has not changed in response to the delivery of the bursts of electrical stimulation to the patient's vagus nerve. 
 
     
     
       19. The method of  claim 15 , wherein adjusting the bursts of electrical stimulation delivered to the patient's vagus nerve based on the analysis of the monitored physiological parameters comprises:
 increasing the bursts of electrical stimulation if the R-R intervals between within the electrical activity of the patient's heart are less than a first selected value, wherein increasing the bursts of electrical stimulation comprises at least one of increasing the voltage of the bursts of electrical stimulation, increasing the frequency of the bursts of electrical stimulation, increasing the pulse width of each pulse of the bursts of electrical stimulation, and increasing the number of pulses per burst of pulses of the bursts of electrical stimulation, and 
 decreasing the bursts of electrical stimulation if the R-R intervals within the Electrical activity of the patient's heart are greater than a second selected value, wherein decreasing the bursts of electrical stimulation comprises at least one of decreasing the voltage of the bursts of electrical stimulation, decreasing the frequency of the bursts of electrical stimulation, decreasing the pulse width of each pulse of the bursts of electrical stimulation, and decreasing the number of pulses per burst of the bursts of electrical stimulation. 
 
     
     
       20. An implantable medical device (IMD) comprising:
 a processor; 
 a pulse generator coupled with the processor for selectively delivering atrial and ventricular pulses; 
 an atrial lead operatively coupled with the processor and the pulse generator; 
 a ventricular lead operatively coupled with the processor and the pulse generator so that cardiac events sensed by the atrial lead or ventricular lead are provided to the processor as data; 
 memory coupled to the processor; 
 computer instructions stored in the memory and executed by the processor, the computer instructions comprising:
 counting V-V intervals, 
 determining whether counted V-V intervals indicates presence of VT/VF, 
 determining lack of A-V synchrony, 
 determining SVT exists, 
 delivering electrical stimulation near or to vagal nerve tissue to slow ventricular rate in response to determining existence of SVT, 
 analyzing the V-V intervals after delivering electrical stimulation near or to vagal never tissue, 
 adjusting the electrical stimulation delivered near or to vagal tissue based on the analysis of the V-V intervals, and 
 terminating the delivery of electrical stimulation near or to vagal nerve tissue after exhausting adjustments to the electrical stimulation.